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gpu: nova-core: export Rust symbols for nova-drm

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Export nova-core's Rust symbols so nova-drm can resolve references to it
when loaded as a module.

This is done by generating declarations and EXPORT_SYMBOL_RUST_GPL()
calls for Rust symbols referenced by nova-drm, and compiling them into
the module as `nova_core_exports.o`.

`nova_core_exports.o` declares every Rust symbol as `extern int`.
Running `gendwarfksyms` on it would compute CRCs from those placeholder
types instead of the real Rust ones, so make MODVERSIONS use this shim
only for the export list, and derive CRCs from `nova_core.o`.

This patch is intended to be a workaround until the build system
supports Rust cross-crate dependencies natively.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://patch.msgid.link/20260622-nova-exports-v5-2-6191773fc977@nvidia.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
This commit is contained in:
Alexandre Courbot 2026-06-22 22:30:08 +09:00 committed by Danilo Krummrich
parent ca524e273c
commit 3b7b7ad78f
3 changed files with 55 additions and 1 deletions
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40
drivers/gpu/Makefile
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@ -14,7 +14,45 @@ obj-$(CONFIG_TRACE_GPU_MEM) += trace/
# system supports cross-crate dependencies natively.
obj-$(CONFIG_NOVA_CORE) += nova-core.o
nova-core-y := nova-core/nova_core.o
nova-core-y := nova-core/nova_core.o nova-core/nova_core_exports.o
obj-$(CONFIG_DRM_NOVA) += nova-drm.o
nova-drm-y := drm/nova/nova.o
# Export Rust symbols from nova-core only if nova-drm actually references them.
nova-core-export-deps := $(if $(CONFIG_DRM_NOVA),$(obj)/drm/nova/nova.o)
rust_needed_exports = \
{ $(if $(strip $(2)),$(NM) -u $(2);,) echo "__DEFINED_RUST_SYMBOLS__"; \
$(NM) -p --defined-only $(1); } | \
awk -v fmt='$(3)' ' \
/^__DEFINED_RUST_SYMBOLS__$$/ { defs = 1; next } \
!defs { if ($$NF ~ /^_R/) needed[$$NF] = 1; next } \
defs && $$2 ~ /(T|R|D|B)/ && $$3 ~ /^_R/ && \
$$3 !~ /_(init|cleanup)_module$$/ && \
$$3 !~ /__(pfx|cfi|odr_asan)/ && \
$$3 in needed { printf fmt, $$3 } \
'
quiet_cmd_exports = EXPORTS $@
cmd_exports = \
$(call rust_needed_exports,$<,$(nova-core-export-deps),EXPORT_SYMBOL_RUST_GPL(%s);\n) > $@
$(obj)/nova-core/exports_nova_core_generated.h: $(obj)/nova-core/nova_core.o $(nova-core-export-deps) FORCE
$(call if_changed,exports)
targets += nova-core/exports_nova_core_generated.h
$(obj)/nova-core/nova_core_exports.o: $(obj)/nova-core/exports_nova_core_generated.h
CFLAGS_nova-core/nova_core_exports.o := -I $(objtree)/$(obj)/nova-core
ifdef CONFIG_MODVERSIONS
# The C export shim declares Rust symbols as `extern int`, so reuse its export
# list but generate symbol CRCs from the Rust object instead of the shim's DWARF.
$(obj)/nova-core/nova_core_exports.o: private cmd_gensymtypes_c = \
$(call getexportsymbols,\1) | \
$(objtree)/scripts/gendwarfksyms/gendwarfksyms \
$(if $(KBUILD_GENDWARFKSYMS_STABLE), --stable) \
$(if $(KBUILD_SYMTYPES), --symtypes $(@:.o=.symtypes),) \
$(obj)/nova-core/nova_core.o
endif

1
drivers/gpu/nova-core/.gitignore vendored Normal file
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@ -0,0 +1 @@
exports_nova_core_generated.h

15
drivers/gpu/nova-core/nova_core_exports.c Normal file
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@ -0,0 +1,15 @@
// SPDX-License-Identifier: GPL-2.0
// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
/*
* Exports Rust symbols from the `nova_core` crate for use by dependent modules.
*
* This is a workaround until the build system supports Rust cross-module
* dependencies natively.
*/
#include <linux/export.h>
#define EXPORT_SYMBOL_RUST_GPL(sym) extern int sym; EXPORT_SYMBOL_GPL(sym)
#include "exports_nova_core_generated.h"